Conventional security labels show tampering with a patterned release to show a hidden word (OPENED, VOID, etc.). Another common design is to use tamper slits or a frangible material, so the security label cannot be removed in one piece; instead it will break into multiple pieces when removed.
Both of the above features are effective if the label is removed. However, if the conventional security label is slit with a knife, the conventional designs do not readily indicate tampering. For example, on a shipping carton, the entire taped seam can be slit to gain access to the contents. In this case, the opposing carton flaps can be repositioned and retaped with clear packing tape.
It is also possible to partially slit the carton seam, remove some of the contents and then re-tape the carton seam. No re-positioning of the flaps is needed, thus making the intrusion harder to detect.